Fluid divider block suitable for use at high pressures

ABSTRACT

The invention is a divider block assembly suitable for use at high fluid pressures. Applicant has found that a sufficiently deep counterbored hole allows a mounting bolt to apply the sealing pressure well below the divider block surface, which can reduce or eliminate the compressive force on the metal around the piston bore, thereby reducing or eliminating distortion of the piston bore of the divider block and providing.

This application is a continuation-in-part application of U.S.application Ser. No. 11/405,383, filed on Apr. 17, 2006, which is acontinuation application of U.S. application Ser. No. 10/816,212, filedon Apr. 1, 2004 and now U.S. Pat. No. 7,096,889, which claims priorityfrom U.S. Provisional Application No. 60/459,403, filed on Apr. 1, 2003,all of which are hereby incorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to high pressure, low volume fluid flowsystems.

BACKGROUND OF THE INVENTION

Without adequate lubrication, industrial tools and machines such ascompressors can be seriously damaged or destroyed. In many applications,a pump pressurizes a lubricant which is then distributed to multiplelubrication points using a device referred to as a “divider block” or“divider valve.” In a divider block, the pressurized lubricant causes aset of pistons to move back and force in within piston bores, the movingpistons opening and closing internal fluids channels, so that a knownvolume of fluid is distributed to multiple outlet channels, once forevery cycle of the group of cylinders. Because the pistons in thedivider block are powered by the pressure of the fluid beingdistributed, no additional source of power is necessary to operate thedivider block.

Divider blocks have been used to distribute lubricating oil tocompressors for about fifty years, and they have changed little sincetheir introduction. Because of the relative simplicity of dividerblocks, users have been confident that divider blocks accuratelydistribute a fixed quantity of lubricant or other fluid to each outletduring each cycle of the divider block. When lubricated equipment fails,a technician will typically check to see that the divider block iscycling, and if it is, then assume that the equipment failure was notcaused by a lack of lubrication. It has been observed that pistonswithin divider blocks occasionally wear out, but that is typicallyattributed to the large number of cycles and the close fit of the pistonwithin the cylinder.

FIG. 1 shows the construction of a typical prior art divider block 100.Divider block 100 is built from multiple sections, including a baseplate 102 and multiple divider block sections 104 mounted on the baseplate 102. Each divider block section 104 includes an internal piston(not shown) within a bore (not shown). The base plate 102 is comprisedof multiple sections, including an inlet section 108 connected to apressurized fluid source (not shown), one or more intermediate baseplate sections 110, and an end section 112. A divider block section 104is mounted on each intermediate base plate section 110.

The inlet section 108, end section 112, and intermediate base platesections 110 include internal channels (not shown) for fluid movementand holes for moving fluid between adjacent sections of base plate 102.Each intermediate base plate section 110 also includes an outlet (notshown) for dispensing the fluid, and holes for moving fluid in and outof the corresponding divider block sections 104.

Divider block sections 104 are typically available in a variety of boresizes. Sizes are indicated as thousandth of a cubic inch displacement,such as sizes 6, 9, 12, 18, 24, and 30. In some divider blocks, inletsection 108 and/or the end section 112 are formed from a block that alsoincludes an intermediate base plate. Additional intermediate base platesections 110 can be inserted, along with corresponding divider blocksections 102, to provide as many fluid outlets as necessary.

As shown in FIG. 1, each divider block section 104 is typically boltedto its corresponding intermediate base plate 110 using two bolts 120.The bolt holes are not positioned along a center line of the dividerblock section 104, because centered bolt holes would interfere withinternal fluid passages. The bolt heads are typically recessed in acounterbore in the divider block section 104. The end section 112, inletsection 108, and intermediate base plates 110 are also bolted togetherusing three bolts with threads on each end and a nut to tighten themanifold pieces together. Another design to bolt the inlet, intermediateand end section base plates 110 together uses hollow bolts with threadson the inside and outside, and solid bolts are inserted into the hollowbolts to manifold the intermediate and end sections together. The insertis threaded into one intermediate base plate 110, and then a bolt (notshown) through the next intermediate base plate 110 is threaded into theinternal threads of the insert. This arrangement allows any number ofintermediate base plates to be connected together.

FIG. 2 shows a base plate 102 including three intermediate base platesections 110 without divider block sections 104. FIG. 2 shows holes 210though which fluid passes between the base plate sections 110 anddivider block sections 104, and threaded holes 212 for receivingmounting bolts 120 (FIG. 1). FIG. 3 shows a side view of a base plate102 of FIG. 1, showing the three intermediate base sections 110, theinput section 108, and the end section 112. Each intermediate basesection 110 includes an outlet port 312. Outlet port 312 typicallyincludes internal pipe threads so that an outlet pipe can screw directlyinto output port 312.

FIG. 4 shows a cross-section of a divider block section 104. Within apiston bore 400 is positioned a piston 402. Piston 402 typicallyincludes two sections 404 of reduced diameter separating three sections406 having a diameter that just fits within bore 400. Fluid can readilypass around sections 404, whereas fluid does not readily pass aroundsections 406, thereby allowing fluid pressure to move piston 402. Thepiston clearance within a piston bore is typically designed to be about0.0003 inches (three ten-thousandths of an inch). A plug 408 is shown atone end of the bore 400. Bolt holes 410 are used for passage of bolts120 that connect divider block section 402 to an intermediate basesection 110, and indicator ports 412 are used to allow oil to eitherpass through the port from passage 414 or to be exposed in the port fortrouble shooting purposes. FIG. 5 shows a front view of the dividerblock section 104 of FIG. 1. FIG. 5 shows bolt holes 410 and plugs 504in indicator ports 412. FIG. 6 shows an end view of a divider blocksection 110 without plug 408, so piston 402 is visible in piston bore400. This end view also shows the thin wall of metal above the piston,which is associated with failure of the piston to dispense accuratevolumes of fluid in high pressure applications.

Over the years, industry has been experiencing unexplained equipmentfailures or reduced equipment life. Examination of the divider blockused to lubricate the failed equipment often shows that the dividerblock is cycling properly, thereby leaving the cause of the failure amystery.

SUMMARY OF THE INVENTION

An object of the invention is to provide a reliable divider block foruse at high pressures.

Applicant has found that at high pressures, conventional divider blocksdeform and may not accurately dispense the required volume of fluid. Thepressure at which divider blocks operate has gradually increased overthe years, and industry was unaware that as the pressure has increased,the accuracy of the volume of fluid dispensed by the divider blocks hasdecreased.

Applicant has found that with increased pressure, piston bores deform,and the pistons can fail to deliver the expected quantity of fluid,causing equipment failure or excess wear because of insufficientlubrication. Because the clearance of the piston within the bore is verysmall to prevent fluid from bypassing the piston, even a slightdeformation of the bore can allow fluid to bypass the piston, thusreducing the amount of fluid delivered. Deformation of the bore can alsocause the piston to chafe against a side of the bore, thereby causingpremature wear of the piston. Because this problem was not recognized,divider blocks have not been designed to resist deformation.

The invention comprises a divider block that resists substantialdeformation at high fluid pressures. Various embodiments can include astronger housing with thicker walls surrounding the bore; the use ofadditional bolts to connect the divider block section to theintermediate base plates to prevent distortion and to distribute torqueevenly to ensure sealing of the o-rings; strengthening the base sectionby increasing its physical size, that is, using more metal to form theinlet, intermediate and end sections; and using larger heat-treated tierod bolts to assemble the base section to decrease flexing and ensuresealing of all o-rings; and carefully tightening all bolts to theirproper torque to prevent deformation, and providing for the connectingbolts counterbores that are sufficiently deep that the force from thetightened bolts does not deform the piston bores, even if the bolts areover tightened. Not all of the measures are required for everyapplication.

Applicant has also found that as the operating pressure increases, itbecomes more important to balance the outlet pressures of the dividervalve. When the outlet pressures are not balanced, pistons can move toorapidly, causing chaffing and premature wear. In accordance with anotheraspect of some embodiments of the invention, divider block outlets arepre-balanced using adjustable pressure valves that maintain a desiredpressure at the outlets. In some embodiments, the divider block isdesigned to require balancing valves at each fluid outlet, unlike priorart divider blocks, which can typically be connected directly to anoutput pipe with or without a balancing valve.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter. It should be appreciated by those skilled in the art thatthe conception and specific embodiment disclosed might be readilyutilized as a basis for modifying or designing other structures forcarrying out the same purposes as the present invention. It should alsobe realized by those skilled in the art that such equivalentconstructions do not depart from the spirit and scope of the inventionas set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, the following description is made with reference tothe accompanying drawings, in which:

FIG. 1 is a front perspective view of a prior art divider block.

FIG. 2 is a front view of the base plate of the divider block of FIG. 1.

FIG. 3 is a side perspective view of the base plate of the divider blockof FIG. 1.

FIG. 4 is a cross-sectional view of a divider block section of thedivider block of FIG. 1.

FIG. 5 is a front view of a divider block section of the divider blockof FIG. 1.

FIG. 6 is an end view of the divider block section of the divider blockof FIG. 1.

FIG. 7 is a front perspective view of a divider block embodyingprinciples of the present invention.

FIGS. 8A and 8B are, respectively, a front view and a side view of abase plate used with the divider block of FIG. 7.

FIGS. 9A, 9B, and 9C are, respectively, a sectional view, a front view,and an end view of a divider block section of the divider block assemblyof FIG. 7.

FIG. 10 shows schematically the fluid flow within the divider block ofFIG. 7 during one part of its cycle.

FIG. 11 shows schematically the fluid flow within the divider block ofFIG. 7 during a part of its cycle following the part shown in FIG. 10.

FIGS. 12A and 12B are, respectively, a front view and a side view of analternative embodiment of a base plate used with the divider block ofFIG. 7.

FIG. 13 is a cross-sectional view of a divider block section of FIG. 9C.

FIG. 14 is a cross section of a divider block that includes counterboresthat extend sufficiently deep into the divider block section toeliminate distortion of the piston bore.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To investigate the problem of compressor failures when the divider blockproviding lubrication to the compressor appears to be cycling normally,applicant built a test stand to measure the volumes of fluid dispensedfrom several commercially available divider blocks at various pressures.Applicant monitored the number of cycles and the nominal output volumeat working pressures of up to about 5000 psi using proflo® monitorsdescribed in U.S. Pat. No. 5,835,372 and commercially available from CCTechnology, Midland, Tex., the assignee of the present application. Theproflo® monitor measures the number of cycles of a divider block and canreport and trend the output volume of the divider blocks at each outletpoint while the system is operating at actual operating pressures.Applicant also measured the actual volume of fluid dispensed into anoutlet path of the divider, using a single inlet, single outlet dividerblock located in the fluid outlet path downstream of the divider blockunder test. A single inlet, single outlet divider block is described inU.S. patent application Ser. No. 10/402,205, which is assigned to theassignee of the present invention and which is hereby incorporated byreference.

The results of applicant's tests were unexpected. Applicant found thatthe output volumes changed drastically at higher pressures. Applicantthen determined that the change in output volume is caused by expansionof the piston bore under the high pressure. The expansion was found tobe a significant fraction of the piston clearance. The clearance betweenthe piston and bore of a typical divider block is about 0.0003 in.Applicant found that the stress of the high pressure caused the thinwall of the divider block bore to expand as much as 0.00017 in. Thisexpansion allows the oil to leak around the piston to a lower pressurepath, thereby changing the amount of fluid that is dispensed with eachpiston cycle and reducing the accuracy of the divider block.

FIGS. 3-6 illustrate some of the problem areas that applicant hasdiscovered in a commercially available, prior art divider blockassembly. FIG. 3 shows that the thickness 322 of intermediate basesections 110 at outlet ports 312 is not great. This thin area allows fordeformation of the metal at high pressure, which allows fluid to passaround the piston and travel a path of least resistance. FIG. 4 showsthat the thickness 420 of material above the bore 400 in the dividerblock section 104 is not great, and is susceptible to deformation athigh pressures. FIG. 4 also shows the relatively thin areas between bore404 and counterbored bolt holes 410 and between bore 404 and inspectionports 412. FIG. 5 shows that bolt holes 410 are not centered on thedivider block surface to prevent interference with internal fluidchannels. Off-centered bolts apply asymmetric forces to the sealsbetween the divider block section 102 and intermediate base plate 110,and can be overtightened in an attempt to reduce leaks. Overtighteningcan cause the piston bore to deform. FIG. 6 shows that the thickness 604of material on the side of the piston bore is relatively small.

The thin wall on the top of the piston shown in FIGS. 4 and 6 expandsand distorts in high-pressure applications, making prior art dividerblocks unsuitable for use at higher pressures. Because lubricationpressures have been increasing in recent years, the industry needs adivider block that accurately dispenses fluid at mid pressure (greaterthan about 1,000 psi) to high pressure service (greater than about 3500psi).

Table 1 below shows calculated stress, strain, and expansion(deformation) of various divider block piston bores at differentpressures. Table 2 shows the characteristics of each of the blocks inTable 1. The stress “S,” strain “σ,” and expansion were calculated asfollows:

S=P*(ID+t)/2t, in which “P” is the pressure in the cylinder in poundsper square inch (psi), “ID” is the inner diameter of the piston bore,and “t” is the thickness of the wall at the thinnest point;

σ=S/E, in which E is the modulus of elasticity, which is equal to31,443,675−34,909.64*T, with T being the temperature in degreesFahrenheit; and

Expansion=σ*ID.

TABLE 1 Block Pressure Number Property 5000 4000 3000 2000 1000 6 S(psi) 4962.5 3970 2977.5 1985 992.5 σ (in/in) 0.000197 0.000158 0.0001187.89E−05 3.94E−05 Expansion 0.350 0.280 0.210 0.140 0.070 ( 1/10,000 in)9 S 5756.135 4604.908 3453.681 2302.454 1151.227 σ 0.000229 0.0001830.000137 9.15E−05 4.58E−05 Expansion 0.486 0.389 0.291 0.194 0.097 12 S7313.462 5850.769 4388.077 2925.385 1462.692 σ 0.000291 0.0002330.000174 0.000116 581E−05 Expansion 0.728 0.582 0.437 0.291 0.146 18 S9028.261 7222.609 5416.957 3611.304 1805.652 σ 0.000359 0.0002870.000215 0.000144 7.18E−05 Expansion 1.078 0.862 0.647 0.431 0.216 24 S12508.33 10006.67 7505 5003.333 2501.667 σ 0.000497 0.000398 0.0002980.000199 9.94E−05 Expansion 1.791 1.433 1.075 0.716 0.358 30 S 13759.3811007.5 8255.625 5503.75 2751.875 σ 0.000547 0.000438 0.000328 0.0002190.000109 Expansion 1.970 1.576 1.182 0.788 0.394

TABLE 2 Inner Diameter of Thinnest Wall Temperature Block Number PistonBore (inches) Section (inches) (Degrees F.) 6 0.177 0.18 180 9 0.2120.163 180 12 0.250 0.13 180 18 0.300 0.115 180 24 0.360 0.090 180 300.360 0.080 180

Table 1 shows, for example, that block number 30, which Table 2 shows ashaving an inner diameter of 0.360 in. and a minimum wall thickness of0.080 in., will expand by 0.000118 in. at 3000 psi operating pressureand by 0.000197 in. at 5,000 psi. These expansions are a significantfraction of the piston clearance of 0.0003 in. and can significantlyreduce dispensing accuracy. Having recognized that the equipment failurecan be caused by inaccurate dispensing at middle to high pressures, adivider block of the present invention can be designed to reducedeformation and improve dispensing volume accuracy.

A preferred embodiment of the invention is capable of deliveringaccurate volumes of oil in high-pressure service, that is, at pressuresgreater than about 3,500 psi. Such a block resists significantdeformation, that is, deformation that causes the accuracy of the blockto vary from the nominal fluid volume by more than 15%. A preferreddivider block reduces deformation to ensure an accuracy of better than15% at pressures of about 3500 psi, more preferably better than 10% at3500 psi, and most preferably better than 5% at 3500 psi. Such blocksalso have improved accuracy at higher pressures, including 5,000 psi.

A preferred divider block capable of reliable operation in high pressureapplications incorporates several changes and additions to the completesystem. Not every embodiment of the invention necessarily includes allof the improvements described below.

FIG. 7 shows a preferred embodiment of the invention referred to as anXD (“extreme duty”) divider block assembly 702. Preferred divider blockassembly 702 includes a base plate 704 and three divider blocks sections706. Each divider block section is preferably attached to the base plate704 using 4 bolts 712, instead of two bolts like in prior art dividerblocks. Using four bolts allows for a symmetric tightening force, whilethe bolt holes do not interfere with internal passages of the dividerblock section 706. Two plugs 714 for each divider block section 706cover an inspection port. Check valves 720, preferably stainless steelpoppet-type valves with integral tube connections, are attached to allfluid outlets.

FIGS. 8A and 8B show a front view and a side view, respectively, ofpreferred base plate 704 without divider blocks sections 706 mountedthereon. Base plate 704 includes an inlet section 802, an end section806, and three intermediate base plate sections 804 a, 804 b, and 804 c,on which three divider blocks sections (not shown) can be mounted. Holes812 pass fluid between intermediate base plate sections 804 and thecorresponding divider block section 706. Threaded bolt holes 814 acceptbolts for attaching divider block sections 706. Holes 816 are formounting the complete divider block assembly.

Attached to balancing valves 720 a-720 f are tubing connectors 820 fortubing that delivers the lubricant to a point of use or subsequentdivider block. The multiple sections of the base plate 704 arepreferably assembled using three tie rod bolts 830 (also referred to asmanifold bolts) and nuts 832. Tie rod bolts 830 are preferably 0.313 in.or larger in diameter and heat-treated. Proper torque is applied to thebase plate manifold bolts to ensure that the bolts are sufficientlytight to resist deformation and flexing from the high pressure and toensure an even force on the o-rings (not shown) between the sections ofthe base plate for proper sealing to prevent leaking. The larger,heat-treated tie rod bolts resist deformation under the extra torqueapplied when tightening them. The proper torque ensures the bolts arestretched to factory specifications during assembly and will notdetrimentally expand after the system is installed on the compressor orpiece of machinery when temperatures and pressures are elevated. Whilethe invention could be used with the prior art-type threaded insert thatfasten each section to the adjacent section, the use of longer boltsthat hold the entire assembly together allows for uniform tightening,and eliminates the problem of stripping threads which occurs with theprior art threaded inserts.

O-rings (not shown) are positioned between all the base plate sectionsand between the check valves 720 a-720 f and their respectiveintermediate base plate sections 804 a-804 c. O-rings are preferablymade of 90 durometer, peroxide-cured Viton, which resists becomingbrittle in high temperature applications and is compatible withsynthetic and mineral based oils. Additional intermediate base platesections 804 can be added, along with additional divider block sections706, as needed to provide additional fluid outlets.

FIGS. 9A, 9B, and 9C show divider block section 706 in more detail. FIG.9A shows a front sectional view, FIG. 9B shows a front view, and FIG. 9Cshows a side view. FIG. 9A shows a piston 916 within a piston bore 918sealed by piston enclosure plugs 914. FIGS. 9A-9C show that dividerblock section 706 is designed with sufficient metal surrounding thepiston bore 918 to eliminate the flexing and distortion when operatingunder high pressures. FIG. 9C shows that, in one embodiment, the headsof bolts 712 are flush with the surface of divider block section 706,that is, in this embodiment divider block section 706 does not includecounterbores for recessing mounting bolts 712, thereby avoiding areduction in thickness of material around bore 918. While this adds tothe overall thickness of diver block assembly 702, applicant has foundthat the additional thickness is acceptable to produce a more accuratedivider block and prevent distortion of the bore from over-tightening.

In prior art counterbores, the bottom of the counterbore is locatedabove the piston bore. Skilled persons have failed to recognize that asthe mounting bolt is tightened, the piston bore is squeezed between thebottom of the counterbore and the base plate and can distort, which inturn causes metering inaccuracy and eventual divider valve failure. Inan alternative embodiment of the invention, the divider block includescounterbores for recessing the mounting bolts, with the counterboresbeing sufficiently deep to minimize or eliminate distortion of thepiston bore.

FIG. 13 shows a cutaway view of a divider block 1302 mounted to baseplate 1302. Bolt 1304 extends through mounting bore 1306 of dividerblock 1302 and threads into base plate 1308. Sealing torque is appliedto bolts 1304 to draw the sealing surfaces of divider block 1302 andbase plate 1308 together. The upper surface 1310 of divider block 1300provides a shoulder that head 1306 of bolt 1304 can engage to providesealing pressure against base plate 1312. When two bolts on both sidesof the piston bore are used, as shown in FIG. 13, the piston boredistortion is less than the distortion of typical divider blocks inwhich only two bolts on one side of the piston bore are used. Excessivetorque is applied to bolts 1304, however, may cause piston bore 1314 todistort because as bolts 1304 are tightened. The distortion of pistonbore 1314 is shown exaggerated in FIG. 13 for illustration.

Applicant has recognized that a sufficiently deep counterbored holeallows a mounting bolt to apply the sealing pressure well below thedivider block surface, which can reduce or eliminate the compressiveforce on the metal around the piston bore, thereby reducing oreliminating distortion of the piston bore of the divider block.Distortion is preferably minimized so that the volume of fluid dispensedis accurate to within 15% at 3500 psi even if excessive torque wasapplied to the bolts.

As shown in FIG. 14, a divider block 1402 includes counterbores 1404that provide shoulders 1406 further from the top surface 1408 of dividerblock 1402 than the prior art counterbore shoulders shown in FIG. 5. Thecounterbore shoulders 1406 are sufficiently below upper surface 1408 toreduce or eliminate pressure on a piston bore 1410 and thereby preventdistortion when bolts 1412 are tightened, or even over tightened, toseal the divider block 1402 against a base plate 1414. In a preferredembodiment, the piston bores do not distort when the fasteners areovertightened by 10%, 20%, 25%, 50% or 100% of the recommended torque,which torque will depend on the size of the bolts.

In the embodiment of FIG. 14, counterbore shoulders 1406 are below thelowermost edge of the piston bore 1400, that is, below the depthindicated by line 1420. In other embodiments, the counterbores do notextend that far. For example, in some embodiments, the counterboresextend at least half the distance between the top of the divider blocksection and the top of the piston bore, that is, below the depthindicated by line 1422. In other embodiments, the counterbore extends atleast the distance between the top surface of the divider block and thetop of the piston bore, that is, at least to the depth indicated by line1424. In still other embodiments, the counterbore extends into thedivider block section to a depth past the depth (indicated by line 1426)of a point ⅓ of the distance from the top of the piston bore to thebottom of the piston bore, past the depth (indicated by line 1428) ofthe midpoint of the piston bore, or past the depth (indicated by line1430) of a point ⅔ of the distance from the top of the piston bore tothe bottom of the piston bore. When describing the depth of thecounterbore to which the counter extends or, equivalently, the positionof the shoulder of the counterbore, relative to the piston bore, it willbe understood that the counterbore extends next to, and not into, thepiston bore and that there is sufficient metal between the piston boreand the counterbore to prevent distortion by the fluid pressure.

Because the mounting pressure or force is applied from the level of thecounterbore shoulder 1406, when the shoulder is sufficiently below thesurface so that much of the compressive force bypasses the piston bore,the piston bore 1410 experiences little or no distortion caused by themounting force from bolt heads 1414.

FIGS. 10 and 11 show schematically how divider block assembly 702functions. FIG. 10 shows internal passages 1020 in the input section802, the three intermediate sections 804 a, 804 b, and 804 c, and theend section 806. Within intermediate sections 804 a, 804 b, and 804 care three pistons 1012 a, 1012 b, and 1012 c within three piston bores1014 a, 1014 b, and 1014 c. The lubricant enters divider block 702 atinlet 1018 in input section 802 and causes pistons 1012 a, 1012 b and1012 c to move back and forth, opening and closing passages, and causesthe lubricant to flow through fluid channels 1020 to outlet check valves720 a-720 f. O-rings 1026 seal the fluid within the channels 1020 as thechannels 1020 pass between the sections, which are held together bybolts as shown in FIG. 8.

In the piston positions shown in FIG. 10, piston 1012 c has justfinished forcing a volume of fluid through check valve 720 f, and thechannels are now set for piston 1012 a to push fluid out through achannel to check valve 720 b as shown in FIG. 11. The design of thefluid paths in divider blocks is well known. The volume of fluiddispensed can be determined from the cross sectional area of the boreand the distance traveled by the piston 1012 c as it pushes the fluid.

FIG. 12A is a front view and FIG. 12B is a side view of an alternativeembodiment for base plate 1202 for use with divider block assembly 702.Base plate 1202 includes an inlet section 1204, an end section 1206, andan intermediate base plate 1208. Inlet section 1204 includes an integralintermediate base plate section for mounting a divider block section706. Similarly, end section 1206 includes an integral intermediate baseplate section for mounting a divider block section 706. Thus, base plate1202 includes only three base components, yet accommodates three dividerblock sections 706. By eliminating two base sections compared to theembodiment of FIGS. 8A and 8B, this embodiment reduces the number offluid connections and therefore reduces the possibility of leaks.Additional intermediate base plate sections 1208 can be added, alongwith additional divider block sections 706, as needed to provideadditional fluid outlets.

Applicant has discovered several problems that make prior art dividerblocks unsuitable for use at high pressures. The preferred embodimentsof the invention described above address these concerns. One problem isthat piston bore walls are too thin in places, which allows the walls todeform under fluid pressure. Another problem is caused by inadequatefastener designs, such as too few mounting bolts or weak tie rods usedto assemble the divider block components. The divider block must beassembled tightly to prevent leakage between the components. Users tryto compensate for an inadequate design by overtightening the fastenersto prevent leaks, and the overtightening can deform the piston bore. Yetanother problem is the failure to balance the output pressures of thedivider block. Each of these problems and some preferred solutions aredescribed in more detail below.

A preferred divider block assembly, such as that shown in FIG. 7,includes a balancing check valve at each working outlet to prevent oil,gas, and/or air from backflowing into the divider block system and tobalance the pressure at the different outlets. In some applications, thebalancing check valves can use Viton sealing elastomers in the form of apoppet seal (poppet check valve). In high temperature applications, thevalve can use a metal-to-metal seal, such as a stainless steel ballseated against a machined sealing surface. The design of a preferredbase plate outlet includes an integral check valve, that is, a checkvalve that is part of the divider block design, as opposed to prior artdesigns in which check valves were optional accessories. For example,one preferred base plate is designed with non-pipe threads and o-ringsealed outlets. These outlets accommodate an o-ring sealing check valve,and the non-pipe threads prevent users from using thread sealingproducts such as Teflon tape or thread sealing liquids which may causeproblems if introduced into the hydraulic circuit.

Add-on balancing valves have been available as a relatively expensiveoption on divider blocks, and balancing valves were considered by manyto be unnecessary on lower pressure systems. Applicant has found that inmany instances, a divider block system does not function reliably inapplications with pressures over 800 psi without the use of thebalancing valves, particularly in applications in which the outputpressure varies greatly, that is, by more than 800 psi or 1000 psi. Inapplications where there is excessive pressure on several of thelubrication points, there is preferably a balancing valve on everyoutlet that has a lower working pressure to ensure the system isbalanced with equal pressures on each outlet.

Without balancing valves, when the system distributes lubrication froman outlet at, for example, at 2000 psi, then progressively changes to anoutlet at 100 psi. The pressure can cause the piston in the low-pressurepiston bore to move too rapidly and contact the end plugs on the dividerblock, causing deformation of the piston and premature failure of thedivider block. Lack of the balancing valve can also cause oil to leakpast the divider block piston to a lower pressure path. When thisoccurs, the lubrication point of higher pressure does not receive theneeded quantity of oil, which in turn causes premature wear or failureof compressor or machinery components.

A preferred divider block, therefore, includes integral balancing valvesthat can incorporate a variety of springs to keep the poppet or ballclosed when oil is not being injected through the outlet. An appropriatespring is chosen to balance the pressure in each outlet to reducepressure differentials within the divider valve assembly. For example,if the divider block system's maximum operating pressure at any outletis 1800 psi, balancing check valves should be installed on all outletsof the system so that each outlet requires a pressure of 1800 psi toopen the valve. For example, if the outlet pressure at one outlet were600 psi, a spring would be installed to provide an additional crackingpressure of 1200 psi so that a total of 1800 psi would be required toopen the outlet valve. This system will then be correctly balanced, andall outlets will see the same pressure, 1,800 psi. Because the design ofa preferred base plate intermediate section requires a check valve atthe exit, the user only needs to choose a spring of the appropriatestiffness to place in each balancing valve, and little or no additionalcost is incurred to balance the system. Also, incorporating check valveswith tube connections into the design of the divider block assemblyeliminates additional leak paths in the system caused by adding thebalancing valves.

An inadequate fastener design is another problem of prior art dividerblocks that is addressed by some embodiments of the present invention.Prior art industry standard divider blocks attached to the base platewith only two screws, and applicant has found that the mounting screwscan easily be over tightened and cause distortion to the divider blockbore. Egg-shaped distortion of the piston bore causes the piston to putexcessive pressure against the back and front of the divider block borewhich in turn causes the divider block to wear and fail prematurely.When the divider block mounting screws are over-tightened, the piston inthe bore cannot move freely, the system pressure becomes elevated andthe piston-to-bore clearance is compromised causing the system to failprematurely, creating wear or failure to the compressor or machinerycomponents. If the lubrication system incorporates a pressure gauge, theoperator can detect the elevated pressure, but 85% of compressor lubesystems are installed without a pressure gauge. A preferred dividerblock of the invention is designed to mount on the base plate with fourmounting screws to evenly distribute the force needed to hold thedivider block in a stable position with equal force spread evenly acrossthe block, thereby eliminating the problems with distortion of the blockand ensuring all o-ring seals between the divider block and base plateare compressed equally for reliable sealing. A preferred embodiment alsoincludes larger, heat-treated tie rods to assemble the base platesections. Such tie rods maintain an adequate torque over time withoutinitial overtightening.

The invention has broad applicability and can provide many benefits asdescribed and shown in the examples above. The embodiments will varygreatly depending upon the specific application, and not everyembodiment will provide all of the benefits and meet all of theobjectives that are achievable by the invention.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

1. A divider block assembly for distributing a low volume of a lubricantat high pressure, the divider block being operated by the pressure ofthe lubricant being dispensed, comprising: a base plate including aninlet section, an end section, and one or more intermediate basesections, each intermediate base section including a lubricant outlet,the base plate being assembled from multiple section using one or morefasteners; one or more divider block sections mounted on the one or moreintermediate base sections, each divider block section having a pistonbore for receiving a piston, a piston, and an outlet passage forlubricant dispensed by the piston as it is moved by the pressure of theincoming fluid, each divider block section having multiple counterboredmounting holes for receiving a fastener, each of the one or morecounterbored mounting holes having a shoulder positioned sufficientlybelow the top surface of the divider block to prevent distortion of thepiston bore when the fasteners are tightened to seal the divider blockto the base plate, the position of the shoulder reducing distortion ofthe piston bore by reducing the compressive force on the metal aroundthe piston bore.
 2. The divider block assembly of claim 1 in whichdistortion of the piston bore is minimized such that the volume oflubricant dispenses at 3500 psi is accurate to within 15%.
 3. Thedivider block assembly of claim 1 in which each divider block section isattached to a corresponding intermediate base section by four threadedfasteners, two on either side of the piston bore.
 4. The divider blockassembly of claim 1 in which each divider block section is attached to acorresponding intermediate base section by two threaded fasteners. 5.The divider block assembly of claim 1 in which the counterbore extendssufficiently into the divider block section to prevent distortion of thepiston bore when the fasteners are tightened to a torque 20% greaterthan a recommended torque.
 6. The divider block assembly of claim 5 inwhich the counterbore extends sufficiently into the divider blocksection to prevent distortion of the piston bore when the fasteners aretightened to a torque 50% greater than a recommended torque.
 7. Thedivider block assembly of claim 8 in which the counterbore extends intothe divider block section to a depth past the depth of a point ⅓ of thedistance from the top of the piston bore to the bottom of the pistonbore.
 8. The divider block assembly of claim 1 in which the counterboreextends into the divider block section to a depth past the depth of themidpoint of the piston bore.
 9. The divider block assembly of claim 8 inwhich the counterbore extends into the divider block section to a depthpast the depth of a point ⅔ of the distance from the top of the pistonbore to the bottom of the piston bore.
 10. The divider block assembly ofclaim 7 in which the counterbore extends into the divider block sectionto a depth past the depth of the bottom of the piston bore.
 11. Thedivider block assembly of claim 1 in which the piston bore isapproximately centered between the long sides of the divider block thatare normal to the surface of the divider block section having holes forpassing liquid to a base plate.
 12. A divider block section for use athigh lubricant pressures, operated by the pressure of the lubricantbeing dispensed, and having a piston bore for receiving a piston, apiston, and a lubricant passage to dispense lubricant pushed by thepiston as it is moved by the pressure of an incoming lubricant, thedivider block section having counterbored holes for receiving fastenersfor attaching the divider block to an intermediate base section, thecounterbore extending from the surface at least to the depth of the topof the piston bore, the counterbore reducing distortion of the pistonbore by reducing the compressive force on the metal around the pistonbore.
 13. The divider block section of claim 12 in which the piston boreis approximately centered between the long sides of the divider blockthat are normal to the surface of the divider block section having holesfor passing liquid to a base plate.
 14. The divider block section ofclaim 12 in which the divider block section includes mounting holes fourthreaded fasteners, two on either side of the piston bore.
 15. Thedivider block section of claim 12 in which the shoulder of thecounterbore is sufficiently far from the surface to prevent distortionof the piston bore when the fasteners are tightened to a torque 50%greater than a recommended torque.
 16. The divider block assembly ofclaim 12 in which the counterbore extends into the divider block sectionto a depth past the depth of a point ⅓ of the distance from the top ofthe piston bore to the bottom of the piston bore.
 17. The divider blockassembly of claim 12 in which the counterbore extends into the dividerblock section to a depth past the depth of the midpoint of the pistonbore.
 18. The divider block assembly of claim 12 in which thecounterbore extends into the divider block section to a depth past thedepth of a point ⅔ of the distance from the top of the piston bore tothe bottom of the piston bore.
 19. A method of assembling a dividerblock assembly for distributing a low volume of a lubricant at highpressure, the divider block assembly including a divider block sectionand a base plate, the divider block assembly being operated by thepressure of the lubricant being dispensed, the divider block sectionhaving a piston bore for receiving a piston, a piston, and a lubricantpassage to dispense lubricant pushed by the piston as it is moved by thepressure of an incoming lubricant, the method comprising: juxtaposingthe divider block section and the base plate; inserting mountingfasteners into counterbored mounting holes in the divider block section,the counterbores extending to a depth equal to at least the depth of thetop of the piston bore; tightening the fasteners to secure the dividerblock section to the base plate.
 20. The method of claim 19 in whichinserting mounting fasteners into counterbored mounting holes includesinserting the mounting fasteners into counterbored holes in which theshoulder of the counterbore is positioned at a depth below the depth ofthe center of the piston bore.
 21. The method of claim 19 in whichinserting mounting fasteners into counterbored mounting holes includesinserting the mounting fasteners into counterbored holes in which theshoulder of the counterbore is positioned at a depth below the depth ofthe bottom of the piston bore.